Durable titania exhaust gas sensor

Abstract

A durable automotive exhaust gas oxygen sensor comprises a ceramic sleeve defining a bore and a titania pellet positioned in the bore against a shoulder thereof. Terminal rods and at least one spacer within the bore securely hold the pellet against the shoulder. The rods, spacer and sleeve are bonded together into a unified assembly by a fused glass seal within the bore that is spaced apart from the pellet.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A durable oxygen gas sensor having a unified construction and comprising: a ceramic tubular body defining an elongated bore comprising an end opening for communicating with a gas for detecting oxygen therein and a terminal-receiving longitudinal portion remote from the gas opening, said body forming a beveled shoulder about the bore facing the terminal-receiving portion and sized and shaped to support a body in said portion against displacement toward said gas opening,   an oxygen-sensitive titania pellet within the bore supported by the shoulder and exposed to gas through the gas opening,   at least two terminal rods suitable for electrically connecting the pellet to an external circuit for measuring an electrical resistance of the pellet, said terminal rods extending through the terminal-receiving bore portion and each rod having an end abutting the pellet and pressing the pellet in the direction of the gas opening,   a ceramic spacer member electrically isolating the terminal rods within the terminal-receiving bore portion, said spacer member abutting and pressing the pellet in the direction of the gas opening, and   means for bonding the terminal rods, spacer member and body together at a location within the bore spaced apart from the pellet, whereby the pellet is securely held against the shoulder by the terminal rods and the spacer member.   
     
     
       2. A durable automotive exhaust gas oxygen sensor comprising: a ceramic sleeve adapted to be mounted through a wall of an automotive exhaust system such that a first end lies in an exhaust gas stream and a second end lies outside the exhaust system, said sleeve defining an axial bore extending between said ends and comprising a gas opening in the first end for exhaust gas communication, a relatively wider terminal-receiving portion opening at the second end and a chamfered shoulder therebetween facing the terminal-receiving portion,   an oxygen-sensitive titania pellet within the terminal-receiving bore portion, said pellet having a generally disk-like shape and a chamfered edge abutting the chamfered shoulder, said pellet having a first major surface communicating with the gas opening and a second opposite major surface facing the terminal-receiving bore portion such that pressure applied to said second surface holds the pellet against the shoulder,   two axial spaced terminal rods extending from the second end through the terminal-receiving bore portion and electrically connected to the pellet for permitting a measurement of a resistance of the titania, each rod having an inner end abutting the pellet second surface so as to urge the pellet against the shoulder,   a ceramic spacer member within the terminal-receiving bore portion spacing apart the terminal rods, said spacer abutting the pellet second surface so as to urge the pellet against the shoulder, and   fused glass seal means spaced apart from the pellet and bonding the terminal rods, the spacer member, and the sleeve together to form a unified assembly wherein the pellet is securely wedged against said shoulder by said terminal rods and said spacer member.   
     
     
       3. A durable oxygen gas sensor comprising: an electrically insulative body defining a cavity having an opening for communicating with an external gas for detecting oxygen therein and an elongated portion apart from the opening, said body forming shouldering means facing the cavity for supporting a body within the elongated portion against displacement toward the gas opening,   a pellet formed of a material whose electrical resistance is responsive to changes in oxygen content of gas in contact therewith, said pellet being supported within the cavity by the shouldering means and exposed to gas through said gas opening,   terminal rods extending through the cavity elongated portion and pressing against the pellet,   an electrically insulative spacer member within the cavity elongated portion between the terminal rods and pressing against the pellet, and   means for bonding the terminal rods, spacer member and body together at a location remote from the pellet, whereby the terminal rods and the spacer member cooperate to securely hold the pellet against the shouldering means.